1. Field of the Invention
This invention relates to installation and removal of large elongated pump motors suspended within a few feet of the floor beneath steam generators in electric power generating plants.
2. Background Information
In a new nuclear power plant design developed by the assignee of the present invention, the steam generators are contained within relatively narrow vertical chambers. The main canned coolant pumps are mounted on the bottom of the steam generator in an inverted position with the elongated motors, each weighing close to 40,000 pounds, extending downward to within a few feet of the floor of the chamber. Thus, access to the pump motor is very limited. Furthermore, the motor is fastened by a motor flange to a pump casing which in turn is welded to the bottom of the steam generator channel head. For removal of the pump motor, the fasteners must be removed and the motor lowered to clear the pump casing flange before it can be moved horizontally out from under the steam generator.
Commonly owned U.S. Pat. No. 5,061,432 entitled "Apparatus for Facilitating the Servicing of Inverted Canned Pump Motors Having Limited Access Space and Restricted Access Time Especially In Nuclear Power Plants" discloses a cart for facilitating installation and removal of such pump motors. This cart has a tall U-shaped frame defining a vertical opening along one elongated side. The cart is provided with rollers so it can be rolled across the floor of the steam generator chamber and into position with the suspended motor received in the elongated opening. Jacks on the cart support the motor while the stud nuts securing the motor to the pump housing flange are removed by workers standing on foldable platforms carried by the cart. The motor is then lowered by the jacks to seat the motor flange on the upper end of the cart.
The cart is then rolled out from under the steam generator and aligned with a narrow, vertical passage between the steam generator and the chamber wall. The cart supporting the motor in an upright position is then lifted by a polar crane up over the top of the steam generator chamber wall and lowered to the operating deck where it is rolled out of containment in an upright position through the main equipment hatch. The pump motor is reinstalled by reversing the above procedure.
While this maintenance cart solves the problem of removing and installing the elongated motor pumps in the very limited space available, it requires the use of the main polar crane and the main equipment access hatch. As it is important to limit plant down time as much as possible, and there are other demands for the main polar crane and the main equipment hatch during an outage, it is desirable to find an alternative procedure and necessary equipment for removing and installing the main coolant pump motors.